Controller for sewing machine

ABSTRACT

A controller for a sewing machine comprising an auxiliary pilepressing plate which is attached at one end to supporting plates and engaged at the other end with a pull bar which is driven by a pedal, a pile-pressing plate kept in contact at one end with the supported end of said auxiliary pile-pressing plate and held at the other end engageably apart from said auxiliary pile-pressing plate, and a pile-pressing part kept in contact with said pilepressing plate.

United States Patent Nomura et al.

[151 3,703,698 [451 Nov. 21, 1972 [54] CONTROLLER FOR SEWING MACHINE [72] Inventors: Fumio Nomura, Hirakata; Yutaka Takamiya; Sakuhiro Mizuno, both of Osaka; Kunio Higashi, Neyagawa; Toshihiro Shimamoto, Kyoto, all of Japan [73] Assignee: Matsushita Electric Industrial Co., Ltd., Osaka, Japan 22 Filed: June 18,1971

211 Appl.No.: 154,582

[30] Foreign Application Priority Data Primary ExaminerLewis H. Myers Assistant Examiner-D. A. Tone AttorneyStevens, Davis, Miller & Mosher [5 7 ABSTRACT A controller for a sewing machine comprising an auxiliary pile-pressing plate which is attached at one end 2: 52 I japan to supporting plates and engaged at the other end with J 1970 Japan "45/64024 a pull bar which is driven by a pedal, a pile-pressing r 0 Japan "45/66896 plate kept in contact at one end with the supported u y apan end of said auxiliary pile-pressing plate and held at the other end engageably apart from said auxiliary pile- [Za :rs. Cll. ..338/108, 338/113, 338/52 pressing plate, and a pile pressing part kept in Contact 1 [OIL C .1101] 9/06 with said pile pressing plate [58] Field of Search ..338/l08,ll3,l01,99, 115, a

338/153, 52 4 Claims, 7 Drawing Figures 25 1g 5 28 g 4 I b0 3/ a Q fli I /0 1 9 7'\\ \/i\\\\\\\ 1 6 i, f-.';-.'5;-'

SHEET 1 [IF 3 p u I u n I I u m sum 2 or 3 (3MP 75: s f f.

PKTENTEDuum m2 PATENTEDNHVZI I972 SHEET 3 [IF 3 P/LE PRESSURE QEQWWQ QVSQSQMN F/ae 0 AMOUNT OF PRESS/N5 0F PEDAL WQDMWWQQ Mum 0 AMOUNT OF PRESSWG 0F PEDAL CONTROLLER FOR SEWING MACHINE This invention relates to a controller for sewing machines.

Controllers for sewing machines heretofore in use which accomplish the control with a foot-operated pile resistor generally have a characteristic tendency that their terminal resistance varies widely with a slight change of the pile pressure in the portion which is subjected to a low pile pressure. With the conventional controllers, therefore, it has been difficult to carry out the low speed control, or the control of the rotational speed of the machine with the pedal pressed by the foot only lightly.

In addition, the controllers of the type described having a foot-operated pedal mechanism are practically not convenient for inspection and adjustment, because the protection of the controlling element and the construction of the pedal as coupled to the base plate for mechanically driving the controlling element limit the accessibility.

The voltage regulating elements, such as carbon pile and filamentary resistors, for these controllers usually develop heat upon supply of electricity. For this reason, the controllers must have large enough overall dimensions and be formed with sufficiently large ventilating holes to dissipate the heat. This brings a danger of the operators foot or some other external object directly contacting the electrically live parts inside.

This'invention is directed to improvements of the controllers through solution of the foregoing problems of the conventional structures.

One object of the present invention is to provide a controller for sewing machines which is capable of smooth control particularly at low speeds by using more than two pile-pressing plates for the pile-pressing mechanism and making the rotational speed of the machine proportional in a linear relation to the amount of pressing of the pedal by the foot.

Another object is to simplify the construction of the pedal and base plate as coupled together and thereby reduce the manufacturing cost and facilitate the adjustment and inspection of the inside of the assembly.

A further object is to limit the heat development of the carbon pile and the associated parts to a uniform level so as to reduce the overall size and make the design compact and eliminate the danger of contact with the electrically charged parts.

These and other objects and features of the present invention will become apparent from the following detailed description taken in conjunction with the accompanying drawings, in which:

FIG. 1 is a vertical sectional view of a controller for sewing machines embodying the present invention, corresponding to the section taken along the line I-I of FIG. 2;

FIG. 2 is a top view of the controller for'sewing machines of FIG. 1, shown with the combined cover pedal removed;

FIG. 3 is a sectional view taken along the line III-III of FIG. 2;

FIG. 4 is a perspective view of radiating metal plates of the controller;

FIG. 5 is a graph showing a general characteristic curve of terminal resistance versus pile pressure;

FIG. 6 is a graph comparing the control characteristics of a conventional controller, an embodiment of this invention, and a theoretically ideal controller with respect to the rotational speed of the sewing machine with the amount of pressing of the pedal; and

FIG. 7 is a graph showing a characteristic curve of pile pressure with the amount of pressing of the pedal in an ideal case.

Referring specifically to FIGS. 1 and 2, there are shown a controlling element 1, a crank mechanism 2 which drives the controlling element, a base plate 3 which accommodates the controlling element, and a pedal 4 to be pressed down by the foot of an operator. This pedal4 is pivotally supported at one end by the base plate 3, so that it can move up and down at the other end. The base plate 3 and the pedal 4 are combined to form the outer contour of the controller. The controlling element 1 consists of a box of a heat-resisting material containing a pile resistor 5 in which is sandwiched between metal plates A and B, designated at 6 and 7, respectively, for heat radiation, and fastened altogether with rivets or screws 8. Supporting plates 9 are fixed to the base plate 3. An auxiliary pile-pressing plate 10, as of a thin leaf spring, is turnably supported at one end by the supporting plates 9 and is engaged at the other end with a pull bar 11. A pile-pressing plate 12, as of a plate spring, is turnably supported, like the auxiliary pile-pressing plate 10, by the supporting plates 9 and is held in contact with the auxiliary plate while its other end is held apart from the auxiliary plate engageably therewith. In contact with this pile-pressing plate 12 is located a pressure-applying part 13 of the pile resistor 5. When the pedal 4- is pressed in the direction indicated by an arrow A (FIG. 1), the pull bar 11 is moved toward the direction indicated by an arrow B (FIG. 2) through a crank mechanism 2. Also provided are return springs 14 which push up the pedal 4, and a return spring 15 which brings the pull bar 11 back after pulling to its original position.

As better shown in FIG. 3, the turnable end of the pedal 4 and the base plate 3 have in between supporting pins 16, seats 17 for receiving the supporting pins 16, which are provided along the edges on both sides of the base plate 3 and have substantially the same diameter as the supporting pins 16, pin-pressing plates 18 which hold the pins 16 in position, and screws 19 which fasten the pin-pressing plates 18 in place. The seats 17 permit the use of a die without side cores at the time of fabricating the base plate 3 from resin, for the reduction of cost. The pedal 4 has through holes 20 to receive the supporting pins 16. Since the pin-pressing plates 18 are fixed to side edge portions of the base plate 3 with the screws 19, lateral holes for receiving the supporting pins 16 are provided. The pin-pressing plates 18 are formed with dogs 21, which serve to prevent the slipping off of the supporting pins 16 which are laterally inserted in position. The pins 16 are formed with grooves 22 in which the dogs 21 of the pinpressing plates 18 fit for the dual purposes of preventing any removal of the pins and keeping said pins in position.

To the inner surface of the end portion of the pedal 4 opposite to the pivoted end is fixed a latch 23 as by a rivet 24. A hook portion 23' of the latch 23 engages with a projection 25 which is provided on the base plate 3. The latch 23 and the associated projection 25 serve to keep the pedal 4 from being urged open upward by the return springs 14 while the pedal 4 remains inoperative without any pressure applied from above. The length a of the hook portion 23' of the latch 23 is shorter than the distance b between the inner surface of the pedal 4 and the latch 23. Moreover, the hook portion is long enough to contact the underside of the projection 25 of the base plate 3. The top of the projection 25 is inclined toward one side, while the bottom is flat. The transverse length of the projection 25 is equal to the width of the latch 23, and there is formed a recess 26 in the center of the projection to permit insertion of a simple tool such as a screwdriver. Thus it looks as if two projections are formed. By inserting a screw driver or the like into this recess 26 it is possible to disengage the hook portion 23 of the latch 23 from the projection 25.

The heat-radiating metal plates A and B, indicated at 6 and 7, are shaped as illustrated in FIG. 4, and the controlling element 1 sandwiched thereby is fixed to the base plate 3 with screws 27, 28. To minimize the contact of the radiating metal plate 6 with the base plate 3, the base plate 3 is formed with a rib 29 to support a part 6' of the metal plate so as to provide a space 30 between the underside of the metal plate 6 and the base plate 3.

The controller and the sewing machine not shown are connected by a cord 31, and the base plate 3 has legs 32.

With the construction above described, the present invention has a primary feature in the pile-pressing mechanism, which will now be discussed. The terminal resistance to pile pressure in a conventional controller for sewing machine, as represented by the curve c in the graph of FIG. 5, exhibits a characteristic tendency that the resistance value changes widely with a minor variation of the pile pressure in the region where the pressure is low. Also, the rotational speed of the sewing machine changes in an inverse proportion to the amount of pressing of the pedal 4, the rotational speed of the machine attains a relationship to the amount of pressing of the pedal 4 as represented by the curve d in the graph of FIG. 6. It will be seen from the curve that the control of the rotational speed of the machine with a small amount of pressing of the pedal, that is, the low speed control, is hardly possible. Then, in order to effeet the low speed control in a stabilized and smooth manner, it is merely necessary to design the controller so that the pile pressure for the amount of pressing of the pedal 4 4 is ideally as represented by the curve e in the graph of FIG. 7. In other words, the controller has only to be such that the pile pressure varies negligibly with the variation in the range of small amount of pressing of the pedal and that the pile pressure is gradually superposed as the amount of pressing of the pedal is increased. In this way the rotational speed of the sewing machine is made proportional to the amount of pressing of the pedal 4 as represented by the straight linefin FIG. 6.

The construction in accordance with the present invention offers an approach to the ideal control characteristic above explained. As the pedal 4 is worked, the pull bar 11 is pulled, and, with an amount of pressing of the pedal below a .certain range, the auxiliary pilepressing plate 10 turns in the direction indicated by an arrow B in FIG. 2 about a fulcrum which is the point where it parts from the pile-pressing plate 12, while, at the same time, the pile-pressing plate 12 and the auxiliary pile-pressing plate 10 turn in the same direction as above about their pivoted ends as their fulcrums. As a result, a pressure is applied by the pile-pressing plate 12 on the pile-pressing part 13, although the pressure is low. As the amount of pressing of the pedal is increased, the portion of the auxiliary pile-pressing plate 10 which is normally away from the pile-pressing plate 12 is brought into contact with the latter and the two plates 10, 12 are altogether turned about their pivoted ends as their fulcrums, until they press the pile-pressing part 13. This pressure is greater than that applied above. Accordingly, the rotational speed of the sewing machine with the amount of pressing of the pedal 4 gains two-step increase as indicated by the curve g in FIG. 6, the curve being nearer to the ideal straight line f than the curve d already explained is. r

It will be obvious that an even closer approach to the ideal control characteristic is possible only by providing a multi-step mechanism in place of the two-step mechanism consisting of a pile-pressing plate and an auxiliary pile-pressing plate as in the embodiment shown, and by choosing suitable material, thickness or length for the plates used in such a pile-pressing mechanism.

Another feature of the present invention lies in the construction of the mechanism for opening the assembly of the pedal 4 and the base plate 3. Now if the pedal 4 in the open state is about to be closed, the hook portion 23 of the latch 23 is caused to slide down over the inclined upper surface of the projection 25 of the base plate 3, as if to escape from the projection 25. As the pedal 4 is further closed, the latch 23 returns by its own elasticity to its original position, the hook portion 23 coming into contact with the underside of the projection 25 When the pedal 4 is to be opened for the purpose of assembling at the factory or inspection of the inside, it is only necessary to close the pedal 4 further by depressing it against the base plate 3. Then, a space will be produced between the end of the hook portion 23' and the outer surface of the base plate 3. A screwdriver or the like may now be inserted into this space and thence into the recess 26 of the projection 25 to unhook and open the pedal in a simple manner. Thus, in the combination of the pedal 4 and the base plate 3, a simple mechanism can attain a positive latching effect to prevent opening of the controller by the operator purposelessly or for curiosity, and can simplify the opening and closing of the controller for assembling at the factory, inspection of the inside, etc. Moreover, it permits the pedal 4 to be turned open after the assembling of it with the base plate 3, so that the depressing distance and the controlling amount can be adjusted with utmost ease.

The third feature of the present invention resides in the construction of the turnable ends of the pedal 4 and the base plate 3. In coupling the base plate 3 and the pedal 4 together, it is only necessary to align the lateral holes defined by the seats 17 and pin-pressing plates 18 of the base plate, with the pedal 4 open with an angle of to the through holes 20 formed in the pedal 4, and

then insert the supporting pins 16 into the holes transversely of the controller. The coupling work is thus most simply accomplished. The lateral holes to receive the supporting pins 16 which serve as pivots for the turning of the pedal 4 and the base plate 3 are formed easily, and the retention and positioning of the supporting pins 16 are simply accomplished as well.

The fourth and last feature of this invention is that the controlling element 1, or the heat-resistant box containing the pile-resistor heat developer 5, is sandwiched between the radiating metal plates A, B, or 6, 7, in a unitary construction and that the radiating metal plates are secured to the base plate 3 with a minimum of contact therewith. This uniformalizes the otherwise localized heat development of the box, limits the temperature rise of the base plate 3 and the pedal 4, and hence reduces the overall dimensions of the controller. Moreover, the number and size of ventilating holes can be reduced to minimize the danger of contact with the electrically live metal parts inside. In a conventional controller not constructed in the manner just described, it has been common that the temperatures of the parts in the vicinity of the pile resistor rise irregularly, thus making the temperature rise on the surface of the base plate and the pedal ununiform and localized disadvantage.

What is claimed is:

l. A controller for sewing machines, comprising: a base plate; a control element mounted on said base plate; a foot operated pedal pivotally connected at one end portion to said base plate; a latch member secured to the inner surface of the other end portion of said pedal; a projection having a flat bottom surface and an inclined top surface formed on said base plate for engaging said latch member, said base plate and pedal forming an intermediate recess therebetween when said latch member is engaged with said projection; a pull bar connected to and driven by said pedal; a pile pressing part connected to said control element; a first pile pressing plate disposed in contact with said pile pressing part; support means supporting one end portion of said first pile pressing plate; and a second pile pressing plate in the form of a leaf spring having one end portion attached to said support means in contact with said one end portion of said first pile pressing plate, the other end portion of said second pile pressing plate engaging said pull bar, and the other end portion of said first pile pressing plate being held engageably apart from said second pile pressing plate.

2. A controller for sewing machines, comprising: a base plate; a control element mounted on said base plate; a foot operated pedal pivotally connected to said plate plate, said pedal being connected to and driving said control element; said base plate having seats along the edges of one end thereof for receiving common supporting pins; said pedal being formed with through holes for receiving said supporting pins; pin pressing plates secured to said edges for covering said seats, said plates being formed with dogs which fit in grooves formed in said supporting pins; a pull bar connected to and driven by said pedal; a pile pressing part connected to said control element; a first pile pressing plate disposed in contact with said pile pressing part; support means supporting one end portion of said first pile ressin lat and a second ile ressi late in the Form 0? a ieai spring having on% en porti o n attached to said support means in contact with said one end portion of said first pile pressing plate, the other end portion of said second pile pressing plate engaging said pull bar, and the other end portion of said first pile pressing plate being held engageably apart from said second pile pressing plate.

3. A controller according to claim 1, wherein said control element comprises a heat resistant box containing a pile resistor sandwiched between heat radiating metal plates to form a unitary assembly, parts of said plates being fixed to said base plate while a part of one of said plates is supported by a rib formed on said base plate.

4. A controller according to claim 2, wherein said control element comprises a heat resistant box containing a pile resistor sandwiched between heat radiating metal plates to form a unitary assembly, parts of said plates being fixed to said base plate while a part of one of said plates is supported by a rib formed on said base plate. 

1. A controller for sewing machines, comprising: a base plate; a control element mounted on said base plate; a foot operated pedal pivotally connected at one end portion to said base plate; a latch member secured to the inner surface of the other end portion of said pedal; a projection having a flat bottom surface and an inclined top surface formed on said base plate for engaging said latch member, said base plate and pedal forming an intermediate recess therebetween when said latch member is engaged with said projection; a pull bar connected to and driven by said pedal; a pile pressing part connected to said control element; a first pile pressing plate disposed in contact with said pile pressing part; support means supporting one end portion of said first pile pressing plate; and a second pile pressing plate in the form of a leaf spring having one end portion attached to said support means in contact with said one end portion of said first pile pressing plate, the other end portion of said second pile pressing plate engaging said pull bar, and the other end portion of said first pile pressing plate being held engageably apart from said second pile pressing plate.
 1. A controller for sewing machines, comprising: a base plate; a control element mounted on said base plate; a foot operated pedal pivotally connected at one end portion to said base plate; a latch member secured to the inner surface of the other end portion of said pedal; a projection having a flat bottom surface and an inclined top surface formed on said base plate for engaging said latch member, said base plate and pedal forming an intermediate recess therebetween when said latch member is engaged with said projection; a pull bar connected to and driven by said pedal; a pile pressing part connected to said control element; a first pile pressing plate disposed in contact with said pile pressing part; support means supporting one end portion of said first pile pressing plate; and a second pile pressing plate in the form of a leaf spring having one end portion attached to said support means in contact with said one end portion of said first pile pressing plate, the other end portion of said second pile pressing plate engaging said pull bar, and the other end portion of said first pile pressing plate being held engageably apart from said second pile pressing plate.
 2. A controller for sewing machines, comprising: a base plate; a control element mounted on said base plate; a foot operated pedal pivotally connected to said plate plate, said pedal being connected to and driving said control element; said base plate having seats along the edges of one end thereof for receiving common supporting pins; said pedal being formed with through holes for receiving said supporting pins; pin pressing plates secured to said edges for covering said seats, said plates being formed with dogs which fit in grooves formed in said supporting pins; a pull bar connected to and driven by said pedal; a pile pressing part connected to said control element; a first pile pressing plate disposed in contact with said pile pressing part; support means supporting one end portion of said first pile pressing plate; and a second pile pressing plate in the form of a leaf spring having one end portion attached to said support means in contact with said one end portion of said first pile pressing plate, the other end portion of said second pile pressing plate engaging said pull bar, and the other end portion of said first pile pressing plate being held engageably apart from said second pile pressing plate.
 3. A controller according to claim 1, wherein said control element comprises a heat resistant box containing a pile resistor sandwiched between heat radiating metal plates to form a unitary assembly, parts of said plates being fixed to said base plate while a part of one of said plates is supported by a rib formed on said base plate. 